H. B. Willman and T. C. Buschbach
The Sharpsboro Member of the Dutchtown Limestone (Templeton and Willman, 1963, p. 55), the upper member, is named for Sharpsboro, Cape Girardeau County, Missouri, a railroad station 5.5 miles southeast of the type section.
The type section of the Sharpsboro Member of the Dutchtown Limestone is located in the Geiser Quarry, 1.25 miles east of Dutchtown (SW NW NW 20, projected, 30N-13E), where the lower 10.5 feet of the Sharpsboro is exposed.
Extent and Thickness
The Sharpsboro Member is 65 feet thick in a well in Pulaski County, but it is 100 feet in the type locality, as shown by a well at Cape Girardeau, Missouri. It apparently thins out rapidly in Jackson County, Illinois, extending only a short distance north of the limit of the Gordonville Member.
The Sharpsboro Member is largely a dark gray, dark brown, or black lithographic limestone. It contains beds of dark gray dolomite, sandy limestone, and dark brown shale. A few beds of light gray dolomite, like that found in the Joachim above, occur near the top. The contact with the Joachim is conformable.The fauna of the Dutchtown Limestone comes largely from the Sharpsboro Member.
TEMPLETON, J. S., and H. B. WILLMAN, 1963, Champlainian Series (Middle Ordovician) in Illinois: Illinois State Geological Survey Bulletin 89, 260 p.
|Stratigraphic Code||Geo Unit Designation|